B.Sc. Biochemistry II Cellular Biochemistry Unit 1 Basics of Cell

Cellular BiochemistryUnit 1

Basics of Cell and cell membrane

B.Sc Biochemistry II

The Cell Theory States:

• As written by Rudolph Virchow (1821-1902):

– All living organisms are made of one or more cells.

– Cells are the basic units of structure and function in all organisms.

– All cells come from previously existing cells.

– The activity of an entire organism depends on the total activity of its independent cells.

Ancient Times

• Ancient peoples are always on the look-out for ways that organisms can be used by them.

• They pass on their understanding orally.

• Some civilizations support “great thinkers” – and philosophers, but they rarely base their thoughts on observation or experiments.

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Timeline of the discoveries, thoughts and technologies that led to the development of the Cell Theory

334 B.C.E - Aristotle

• Greek philosopher, Aristotle, begins to observe nature.

• He classifies all known organisms as either a Plant or Animal.

• He writes that living things can arise spontaneously from non-living matter.

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1268 – 1st Eyeglasses

• Roger Bacon, an English friar makes reference to a pair of eye glasses.

• This means that glass is being developed and used in a way that makes it easier to see small things.

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1500’s

• Most European’s think that knowledge is unchangeable and should not be questioned.

• To find answers about nature, they look to the original teachings of Aristotle.

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1590 – 1st Microscope

• Zacharias Janssen, a Dutch eyeglass maker, makes the 1st microscope by placing two lenses on top of one another to make extra-large images.

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1600’s

• People start to question the origins of life.

• Many begin to suggest that life can only come from other forms of life rather than through spontaneous generation (as was suggested by Aristotle). This only took about 2000 years!

• William Harvey says that maggots do not come from the meat itself but from tiny eggs too small to be scene.

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William HarveyEnglish Physician

1578-1657

1665 – 1st Cells Seen

• Robert Hooke (1635-1703) publishes a

book that shows illustrations of tree bark

lining as seen through a simple compound

(2 lens) microscope.

He observed pieces of cork from the bark of a cork tree under the microscope.

- His observations led him to coin the word “cell.”

- “Cell”- means little rooms in Latin

- He compared the small boxes to the small rooms that monks lived in

• Wrote and published “Micrographia”

• Known as the “English Father of

Microscopy”

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1667 – Species Defined

• John Ray (1627-1705) defines a “species” as a set of individuals that can reproduce their own kind.

• The beginning of the end of spontaneous generation!

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1578-1657 3

1668 – 1st Experiments about origins of maggots

• Francesco Redi (1626-1697) conducts experiments to prove that maggots do not appear in meat if flies cannot land on it!

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1674 – 1st Microscopic Beasties Seen!

• Anton van Leeuwenhoek (1632-1723) reports being able to see tiny beasties (0.002 mm) using a simple single-lens microscope.

• 1673: He looked at pond scum under the microscope and discovered small organisms he called animalcules or little animals (Protists)

- 1676: discovered bacteria

• He also observed blood cells from fish, birds, frogs, dogs, and humans

• Therefore, it was known that cells are found in animals as well as plants

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1753 – Birth of Classification

• Carolus Linnaeus (1707-1778) begins to show people the great diversity of living things by exploring methods of classifying them into 5 main Kingdoms.

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1770 – Advancement of Microscopes

• Microscopes become sturdier and easier to use.

• Flaws in glass production still causes images to be blurry and have coloured halos.

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1800’s – Support for Science Grows

• Lots of interest in science

• Public lectures are popular

• The wealthy mount expeditions to collect new specimens

• The HMS Investigator goes on a 5 year voyage of discovery.

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1809 – 1st Science Texts for Students

• Jane Haldimand (1769-1858) writes textbooks for young people to learn about science.

• Terms such as “cell”, “cellular system” and “Cellular tissue” appear in the book.

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1820’s – Better Glass = Better Lens

• Microscope quality improves with the production of better glass.

• Many English companies compete to produce the best microscope.

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1825 – Book “Cells from Cells”

• Francois Vincent Raspail (1794-1878) wrote a book called (translated from Latin) “Every cell is derived from a preexisting cell”.

• This again puts to rest the idea of spontaneous generation.

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1830 – Cells are studied

• Biology is becoming an important science and the body of knowledge is growing, especially since the improvement of microscopes.

• Scientists begin to study the cell extensively!

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1831 – Nucleus of Cell Found

• Robert Brown (1773-1858) is the 1st to consider the nucleus as a regular part of a living cell.

• The nucleus is still hard to see though without the invention of the electric light for his microscope.

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1838 – Plant cells!

• Matthias Jacob Schleiden (1804-1881) makes the claim “All plants are made of cells”.

• Cells are alive!

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1839 – Animal cells!

• Theodor Schwann (1810-1882) makes the claim “All animals are made of cells”.

• “All living things are made of cells”

• Cells are the basic building blocks of life!

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1845 – Cell Basic Unit of Life

• Alexander Carl Heinrich Braun (1805-1877) makes the claim:

“The cell is the basic unit of life”.

• Cells are made of protoplasm enveloped by a flexible membrane.

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1850’s

• Biological knowledge advances, especially in the areas of medicine, botany and zoology!

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1856 – Staining technique developed

• 18 year old, William Henry Perkin (1838-1907) develops a new purple dye for staining cell parts making it easier to see cell parts with a microscope.

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1858 – Article on Evolution

• Charles Darwin (1809-1882) & Alfred Wallace (1823-1913) read their article on “Tendency of species to form variations”.

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1858 – Cell Theory Outlined

• Rudolph Virchow (1821-1902) develops his Cell Theory that is still largely accepted today.

• He is known as the

“Father of Pathology.”

• Discovered that all living cells come only from other living cells

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1860’s – The end of the “Spontaneous Generation” debate

• Louis Pasteur (1822-1895) conducts a series of experiments that once and for all put to rest the idea of spontaneous generation and concluding that living organisms do not arise from non-living matter.

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The Cell Theory

• Major Contributors:

• Matthias Schleiden

• Theodor Schwann

• Rudolph Virchow

The Cell Theory

The 3 Basic Components of the Cell Theory were now complete:

1. All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39)

2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39)

3. All cells are produced by the division of preexisting cells. (Virchow)(1858)

Modern Cell Theory

• Modern Cell Theory contains 4 statements, in addition to the original Cell Theory:– The cell contains hereditary information(DNA) which is passed on from

cell to cell during cell division.

– All cells are basically the same in chemical composition and metabolic activities.

– All basic chemical & physiological functions are carried out inside the cells.(movement, digestion,etc)

– Cell activity depends on the activities of sub-cellular structures within the cell(organelles, nucleus, plasma membrane)

How Has The Cell Theory Been Used?

• The basic discovered truths about cells, listed in the Cell Theory, are the basis for things such as:– Disease/Health/Medical Research and Cures(AIDS, Cancer,

Vaccines, Cloning, Stem Cell Research, etc.)

Discoveries Since the Cell

Theory

ENDOSYMBIOTIC THEORY

• In 1970, American biologist, Lynn Margulis, provided evidence that some organelles within cells were at one time free living cells themselves

• Supporting evidence included organelles with their own DNA

• Chloroplast and Mitochondria

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Review Facts About Living Things

What Are the Main Characteristics of organisms?

1. Made of CELLS

2. Require ENERGY (food)

3. REPRODUCE (species)

4. Maintain HOMEOSTASIS

5. ORGANIZED

6. RESPOND to environment

7. GROW and DEVELOP

8. EXCHANGE materials with surroundings (water, wastes, gases)

Characteristics of All Cells

• A surrounding membrane

• Protoplasm – cell contents in thick fluid

• Organelles – structures for cell function

• Control center with DNA

Cell Size and Types

• Cells, the basic units of organisms, can only be observed under microscope

• Three Basic types of cells include:

Animal Cell Plant Cell Bacterial Cell

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Cell Size

Question:Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse?

Factors Affecting Cell Size

• Surface area (plasma membrane surface) is determined by multiplying length times width (L x W)

• Volume of a cell is determined by multiplying length times width times height (L x W x H)

• Therefore, Volume increases FASTER than the surface area

Cell Size

• When the surface area is no longer great enough to get rid of all the wastes and to get in enough food and water, then the cell must divide

• Therefore, the cells of an organism are close in size

Cell Size

Question:Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse?

About the same size, but …

The elephant has MANY MORE cells than a mouse!

Multicellular Organisms

• Cells in multicellular organisms often specialize (take on different shapes & functions)

Cell Specialization

• Cells in a multi-cellular organism become specialized by turning different genes on and off

• This is known as DIFFERENTIATION

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Organization Levels of Life

Atoms to Organisms

LEVELS OF ORGANIZATION

Nonliving Levels:

1. ATOM (element)

2. MOLECULE (compounds like carbohydrates

& proteins)

3. ORGANELLES (nucleus, ER, Golgi …)

LEVELS OF ORGANIZATION

Living Levels:

1. CELL (makes up ALL organisms)

2. TISSUE (cells working together

3. ORGAN (heart, brain, stomach …)

4. ORGAN SYSTEMS (respiratory, circulatory …)

5. ORGANISM

ATOMS MOLECULES ORGANELLES

Nonliving Levels

CELLS – life starts here TISSUES – Similar cells working together

Living Levels

ORGANSORGAN SYSTEMS ORGANISM

Different tissuesworking together

Different organsworking together

More Living Levels

Cell Types

• Prokaryotic

• Eukaryotic

Prokaryotes – The first Cells

• Cells that lack a nucleus or membrane-bound organelles

• Includes bacteria

• Simplest type of cell

• Single, circular chromosome

• First cell type on earth

• Cell type of Bacteria and Archaea

• Nucleoid = region of DNA concentration

Eukaryotes

• Cells that HAVE a nucleus and membrane-bound organelles

• Includes protists, fungi, plants, and animals

• More complex type of cells

Eukaryotic Cell

Contain 3 basic cell structures:

• Nucleus

• Cell Membrane

• Cytoplasm with organelles

Similarities between plant cells and animal cells

Both have a cell membrane surrounding the cytoplasm

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Both have a nucleus

Both contain mitochondria

Differences between plant cells and animal cells

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Animal cells Plant cells

Relatively smaller in size

Irregular shape

No cell wall

Relatively larger in size

Regular shape

Cell wall present

Differences between Plant Cells and Animal Cells

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Animal cells Plant cells

Vacuole small or absent

Glycogen as food storage

Nucleus at the center

Large central vacuole

Starch as food storage

Nucleus near cell wall

CELL WALL

• Because a lipid–protein plasma membrane of less than 10-nm thickness can be expected to offer only minimal protection for a cell’s contents, it is not surprising that “naked” cells are extremely fragile structures.

• The cells of nearly all organisms other than animals are enclosed in a protective outer envelope.

• Protozoa have a thickened outer coat, whereas bacteria, fungi,and plants have distinct cell walls.

• The cell wall is the tough, usually flexible butsometimes fairly rigid layer that surrounds sometypes of cells.

• It is located outside the cell membrane andprovides these cells with structural support andprotection, and also acts as a filteringmechanism.

• A major function of the cell wall is to act as apressure vessel, preventing over-expansion whenwater enters the cell. They are found in plants,bacteria, fungi, algae, and some archaea. Animalsand protozoa do not have cell walls.

• The materials in a cell wall vary between species, and in plants and fungi also differ between cell types and developmental stages.

• In plants, the strongest component of the complex cell wall is a carbohydrate called cellulose, which is a polymer of glucose. In bacteria, peptidoglycan forms the cell wall.

• Archaean cell walls have various compositions, and may be formed of glycoprotein S-layers, pseudopeptidoglycan, or polysaccharides.

• Fungi possess cell walls made of the glucosamine polymer chitin, and algae typically possess walls made of glycoproteins and polysaccharides.

• Unusually, diatoms have a cell wall composed of silicic acid. Often, other accessory molecules are found anchored to the cell wall.

References

• Images references:

1. http://commons.wikimedia.org/wiki/File:Goya_Self_portrait_with_spectacles_%28Musee_Goya_

Castres%29.jpg

2. http://micro.magnet.fsu.edu/primer/museum/janssen.htmla

3. http://papapipi.com/spontaneous-generation-vs-biogenesis/

4. http://www.desktopclass.com/education/fafsc/two-to-five-kingdom-classification-systems-f-sc-

biology.html

5. www.antique-microscopes.com/kellner/kellner1.html

6. http://zeisshistoricasociety.org/microscopes/

7. http://www.kidsbiology.com/biology_basics/cells_tissues_organs/cell_history_discovery4.php

8. http://en.wikipedia.org/wiki/White_blood_cell

9. http://papapipi.com/tag/plant-cell

• Reading references:

• Cell and Molecular Biology, 6th Ed By Karp -

http://commons.wikimedia.org/wiki/File:Goya_Self_portrait_with_spectacles_(Musee_Goya_Castres).jpg

http://micro.magnet.fsu.edu/primer/museum/janssen.htmla

http://papapipi.com/spontaneous-generation-vs-biogenesis/

http://www.desktopclass.com/education/fafsc/two-to-five-kingdom-classification-systems-f-sc-biology.html

http://www.antique-microscopes.com/kellner/kellner1.html

http://zeisshistoricasociety.org/microscopes/

http://www.kidsbiology.com/biology_basics/cells_tissues_organs/cell_history_discovery4.php

http://en.wikipedia.org/wiki/White_blood_cell

http://papapipi.com/tag/plant-cell